U.S. Pat. No. 3,090,746 (1963) of F. Markert et. al. discloses a method for cracking hydrocarbons in a fluidized layer of fluidized system. A method was found to avoid the problem of pyrolysis products coating out on surfaces of a cyclone separator. By keeping a solid particulate phase of high temperature particles nearest the interior surface of the outside wall of the cyclone, it was possible to avoid carbonaceous buildup in the cyclone separator.
U.S. Pat. No. 3,273,320 (1966) of L. J. Delaune et. al. discloses a cyclone separator for high temperature operations. A specially designed cyclone outlet tube (made from refractory materials such as alumina, magnesia, beryllium and silicon carbide) is disclosed to provide free movement for thermal expansion to minimize internal stress concentration. These materials are also disclosed to be useful on the interior surface of a cyclone separator. The invention appears to be directed to overcoming stresses that would otherwise arise as a result of expansion and contraction at operating temperatures in the range of between 1093.degree. C. (2000.degree. F.) and 1760.degree. C. (3200.degree. F.). The outlet tube is concentric to the interior of outside walls.
Not disclosed in U.S. Pat. No. 3,273,320 (1966) is the use of an off centered outlet tube which provides benefits to be discussed later in this specification.
U.S. Pat. No. 3,572,011 (1971) of Gunnar Wilhelmsson discloses a filtering apparatus having a rotatable filter drum with a cylindrical filter surface mounted within a housing which introduces material in a swirling pattern so as to swirl into contact with and thru the filter surface. Also disclosed is a means for removing material from the filter surface. This apparatus in no way suggests separation of vapors and particles in the sense of a cyclone separator and is considered non analogous art except that it arguably may disclose an off centered outlet tube.
U.S. Pat. No. 4,070,250 (1978) of Charles K. Choi discloses a pyrolysis of carbonaceous materials in a double helix cyclone. The inlet to the cyclone has three separate pathways. The first pathway nearest the exterior wall of the cyclone is for a high velocity particulate/vapor stream, wherein the heated particulates provide a source for heat. The next stream adjacent to and spaced from the particulate/vapor stream is a low velocity stream of carbonaceous material. And spaced apart from the carbonaceous vapor stream is a third stream which is preferably at an angle to the carbonaceous vapor and spaced inwardly toward the vapor outlet tube. The three streams react to undergo pyrolysis reactions and then are separated into vapors and solid particles. The outlet tube is substantially concentric to the cyclone body. Carbon buildup along the wall is disclosed to be avoided by having a high velocity high temperature particulate stream nearest the interior surface of the outside cyclone wall.
U.S. Pat. No. 4,101,412 (1978) of C. K. Choi discloses an integrated system for the pyrolysis of carbonaceous materials. A stream of carbonaceous material is tangentially introduced at a high velocity along the path formed by the curved surface of the cyclone reaction/separation zone. Also introduced to the cyclone reaction/separation zone is a high velocity high temperature stream of a particulate source of heat contained in a carrier gas. The particulate heat source penetrates the stream of carbonaceous material to initiate pyrolysis of carbonaceous components. In essence two separate streams are introduced one at an angle to the other into a cyclone separator. In FIGS. 2 & 3 of this reference, there is disclosed a somewhat off centered cyclone outlet tube with respect to the interior of a cyclone separator.
U.S. Pat. No. 4,151,044 (1979) of C. K. Choi discloses substantially the same information as was disclosed in U.S. Pat. No. 4,070,250 (1978) discussed hereinabove.
U.S. Pat. No. 4,212,653 (1980) of W. B. Giles discloses a process and apparatus for separating particulate matter from a gaseous medium. Two different vapor streams are disclosed as being introduced into a cyclone concentrically with respect to a vapor outlet tube. One of the streams, substantially particulate free, is introduced so as to form a swirling phase of substantially contaminate free gas immediately surrounding the outlet tube. The other stream, a vapor having particulate, is introduced concentrically with the outlet tube but at a location spaced away from the first stream of swirling gas. The inventive feature is that by having a substantially contaminate free vapor immediately adjacent the outlet tube provides better separation of the particles from the gaseous vapor components.
The cyclone disclosed by Giles is substantially different from any cyclone contemplated by the instant invention in so far as Giles is attempting to use two vapor streams to bring about an improved separation of particulates present in one of the streams. The additional circumferential wall inserted in a cyclone contemplated by the instant invention is not there as a means for introducing a second vapor stream. It is serving a purpose entirely different and distinct from any purpose disclosed by Giles.
U.S. Pat. No. 4,246,013 (1981) of Andrew Truhan et. al. discloses a cyclone type air-particle concentrator and collector wherein a dirty gas stream is subjected to two distinct skimming operations. One of these operations is between the gas inlet scroll and the outlet tube and the other at the exit of the gas discharge scroll. More than one outlet for a vapor stream is provided so that the vapor stream with reduced particulate concentration is removed in two separate streams one between the gas inlet scroll and the outlet tube and the other at the exit from the gas discharge scroll.
This reference of Andrew Turhan in no way discloses off-setting at least a portion of the exterior surface of the outlet tube for vapors from being substantially centrosymmetric with respect to the longitudinal axis (defined hereinafter) of the cyclone.
U.S. Pat. No. 4,344,783 (1982) of Otto Helnemann et al discloses a heat exchange cyclone having several partial spiral or scroll inlets wherein the spirals are one above the other and decrease downward toward the material discharge opening. In other words, the spirals of different portions of the inlet have a different length which decreases downwards. The uppermost partial spiral extending over peripheral angle of at least 180.degree. and the lower most partial spiral extending over a peripheral angle of at least 90.degree.. The purpose of the disclosed scroll inlet designs is to substantially reduce the overall volume weight of the cyclone for substantially the same pressure loss and degree of separation. Each partial spiral of the scroll inlet is about a common axis, the longitudinal axis of the exchange cyclone.
This reference of Otto Helnemann et al. in no way discloses off-setting at least a portion of the exterior surface of the outlet tube for vapors from being substantially centrosymmetric with respect to the longitudinal axis of the cyclone.
With diminishing sources of crude supplies, there is an increasing trend towards reduced crude conversion. Reduced crude conversion involves feedstocks that generally have very high metals and very high Conradson carbon precursors. Catalytic cracking of such feeds require separation of particulate catalysts or sorbents from vapors. The art teaches that if there is a high concentration of particles along the exterior wall of a cyclone separator then carbonaceous deposits on the wall of the cyclone tend to be reduced and substantially avoided. See U.S. Pat. Nos. 4,070,250 (1978) and 4,151,044 (1979) discussed infra. For an example of a process which converts reduced crude of high Conradson Carbon and metals content into a suitable fluid catalytic cracking feedstock, see U.S. Pat. No. 4,243,514 (1981) of Bartholic.
Unfortunately these solutions in the prior art do not work particularly well in more recently used hydrocarbon conversion processes such as in the processing of heavy oils, or a metals removal process by means of sorbents, because one of the things that one tries to do in these processes is to remove as many of the particulate components as possible from a vapor before it enters a cyclone. This is in fact the goal of vented risers disclosed in the following U.S. Pat. Nos.: 4,070,159 (1978) of G. D. Myers et al., 4,390,503 (1983) of P. W. Walters et al. and 4,066,533 (1978) of G. D. Myers et al. Removing from a vapor/particulate stream as many of the particulate components as possible prior to introducing such a stream into a cyclone lessens attrition of the particulates, wear and tear on the cyclone, and may eliminate the necessity for secondary cyclones otherwise required.
Accordingly, there is no method taught in the art which focuses on solving the problem of carbonaceous deposit buildup in a cyclone during separation of paticulates from a hydrocarbon conversion product resulting from feeds of high Conradson carbon precursor content.
"Hydrocarbon conversion processs" is intended to mean for purposes of this specification and claims any process wherein a hydrocarbon feedstock, a coal liquifaction product or feedstock, or shale oil product is contacted with particulate matter to alter in some way some characteristic of such a feedstock. Some examples of such processes are the following: the ART Process in U.S. Pat. No. 4,243,514 (1981) of Bartholic, reduced crude conversion in U.S. Pat. No. 4,332,673 (1982) of G. D. Myers, fluid catalytic cracking, fluid coking, reforming and the like.
"The longitudinal axis of a cyclone" is intended to mean throughout the specification and claims the central axis in the cyclone about which a separation zone is substantially centrosymmetric, e.g. cylindrically symmetric. The separation zone is that location wherein vapors and solids are separated into particulates and vapors by inertial forces, commonly referred to as centrifugal forces.
"Tangential inlets for vapors and solid stream mixtures" is intended to mean any inlet which introduces such a stream into a cyclone separator at an angle transverse to the longitudinal axis of the cyclone. Common transverse angles for example, are anywhere from about 70.degree. to 110.degree..